1. Field of the Invention
This invention relates to synchro systems and more particularly to circuitry for driving a plurality of synchros with high acceleration, little power dissipation, and dynamic characteristics that are independent of the number of units driven.
2. Description of the Prior Art
As well known, the synchro is in essence a small AC machine used for the transmission of angular position data. Each unit may comprise a stator carrying three similar windings distributed in slots having axes displaced from one another by 120 degrees, and a rotor with two salient poles and a single winding. The three stator windings may be connected together in either wye or delta. Typically, a transmitting synchro will be connected to a receiver or follower by interconnecting the stator and rotor windings. AC power is applied to the rotor windings and the rotor of the transmitting synchro is commanded to a particular position either manually or otherwise. This effects the generation of current in each of the stator windings of the transmitting synchro and this current flow in the interconnected stator windings of the receiver forces the rotor of the receiver to assume a position substantially identical to the position commanded of the transmitting synchro.
The present invention is concerned with the means for controlling a plurality of synchro receivers from a single command position. In the past, this has been done electronically and it has also been done mechanically. Difficulties arise when one is interested in driving a plurality of receivers, because considerable power or torque is needed in order to effect the desired response.
It is known that in order to "zero" a synchro one shorts out a pair of stator windings and the rotor will then move to either the electrical zero or electrical 180 degree position. Identification of the particular position is a simple matter and the unit is then calibrated to function from this established point. Considerable torque is generated in the rotor when such a shorted condition is imposed; however, to date, little use has been made of this fact other than to initially position such units.